This invention is related to straddle-cutters, that is, apparatus for cutting two parallel surfaces on opposite sides of a workpiece in a single cut. Two side cutters spaced at a precise distance, machine the two sides of the workpiece simultaneously. For example, brake rotors are machined in this manner. Usually commercial forms of such a device use hydraulic power for moving the cutters into and out of position.
The broad purpose of the present invention is to provide an improved straddle-cutting apparatus using pneumatic power, and a combination of Belleville springs.
Currently industry uses hydraulic fluid/air over hydraulic fluids to actuate piston/cylinders to extend and retract a straddle-cutting tool. Filters, valves, and piping fittings are required to move the fluids and produce the necessary pressures to activate hydraulic piston and cylinders. As the cutting force is applied to the workpiece, a reactionary force in the other direction acts upon the cutters. Liquids have the nature to drift or collapse under applied pressures. Consistencies for dimensional control may be compromised in quality for statistical process controls.
Hydraulic vessels run higher-pressure levels and response times than mechanical advantage devices. Hydraulics used for this application also requires programmed timing for the response.
The preferred embodiment of the invention employs a pair of cutting tools spaced on opposite sides of the cutting position of a workpiece. At least one of the cutting tools is movable toward one face of the workpiece for a cutting motion and then retracted by a pneumatic cylinder. An axially movable shaft moves the cutting tool. The pneumatic cylinder moves a lever to move the shaft to retract the tool. A stack of Belleville washers, mounted around the shaft, return the shaft to extend the cutting tool.
The preferred straddle-cutter provides several advantages over the prior art. It provides a cleaner work environment, and reduces areas for potential hydraulic leaks by eliminating the use of hydraulic oil. The preferred apparatus requires fewer tubular piping and connections, fewer pressure fittings and reduces service calls. The preferred apparatus functions in a factory using industry standard air pressure. No new pressures or factory installations are required. The manufacturer sets the standard of air pressure utilized at the cutter by stamping the requirements directly into the housing.
The mechanical advantage is more reliable because direct mechanical contacts between the internal mechanical devices are used. There are no internal leaks or slippage. A manufacturing advantage exists because reliable product quality is available through reliable management and reduction of the equipment down time. The product holds product dimensions, harmonic surfaces and run-outs to industry standards. Presetting the tooling lends to industry, “lean manufacturing”.
All external components and details attached to the cutter housing are industry standard items, allowing the user to comparatively shop for replacements, and to develop its own inventories of spare parts based upon usage. The products internal design focuses against the various backlashes, and deflections in loadings produced in manufacturing by engineering their details and assemblies to directly access the linear and axial movements associated with resultant forces.
Further advantages are that the preferred straddle-cutter provides the ability to consistently return the cutting tool to the material-removal position. Programming and response time are eliminated, allowing for more product manufactured per work shift. The cutter can maintain a constant force despite changes in a mechanical system resulting from wear, relaxation or thermal change.
At rest, the cutting tool is in the closed, material-removal position. Proper product dimensional control is given to the machinist in an external, manually controlled turning cartridge capable of maintaining relatively small positional tolerances. The cartridge can be adjusted rather than the entire tool. This rest position may also be gaged for final dimensional manufacturing size by the finished product.
When clean air is supplied, the tool opens to a clearance position unable to cut or remove material. This enables the cutter housing holding the cutters to retract back to a home position without causing damage to the finished product surface. At this point, the finished product is unloaded and the next unfinished product is loaded.
Still further objects and advantages of the invention will become readily apparently to those skilled in the art to which the invention pertains, upon reference to the following detailed description.